Security agents are investigating a Russian scientist for allegedly trying to smuggle out of Russia materials that could be used in building a biological or bacteriological weapon, the scientist and his co-workers said Friday.

Russia on Monday announced that 10 people have been arrested in the killing of journalist and Kremlin critic Anna Politkovskaya, including law enforcement officers and a Chechen crime boss accused of organizing the slaying.

A video that remained secret for nearly three years after the horrific Beslan hostage crisis has cast new doubt on official conclusions about what led to the deaths of 334 people, more than half of them children, during one of Russia's worst terrorist attacks.